The present invention relates to the use of compositions that are stable on the body-facing materials of disposable absorbent articles, such as diapers, training pants, adult incontinence products, underpants, feminine care products, nursing pads, wound dressings and similar articles having absorbent capacity. Unexpectedly, the compositions are stable despite not including immobilizing agents previously believed necessary for stability on the body-facing materials. Consequently, the compositions are also simplified, i.e. contain fewer ingredients, from previously known compositions. The viscosity, hardness and overall stability of the simplified compositions were unexpected based on previously taken approaches to delivering a composition from a body-facing material of an absorbent article.
Absorbent articles such as diapers, training pants, incontinence products and feminine care products are worn such that they are in direct contact with the skin of the wearer. An unavoidable consequence of the use of absorbent articles is that the skin is exposed more directly to various physical and biological insults. Consequently, the barrier function of the skin covered by the absorbent article is put at risk. In order to provide disposability, absorbent articles are primarily constructed of nonwoven materials. Even though nonwoven materials are engineered to have soft hand and drape, they rub against the skin and there is friction. Such friction constitutes one form of physical insult to the skin barrier. Friction against the skin barrier also occurs with the use of absorbent tissues and wipes. Absorbent tissue and wipe products are frequently used for cleansing the skin areas covered by absorbent articles. Absorbent tissue and wipe products are necessary for removing biological waste materials from the skin.
In addition to these physical insults, skin covered by absorbent articles is also frequently exposed to biological insults. Biological fluids, such as urine, feces, vaginal secretions and nasal secretions, may contain a variety of components that can damage the skin barrier. Examples of these components include proteases, lipases and bile acids. Once the skin barrier is compromised, these components, in addition to other constituents of biological fluids, can initiate or exacerbate inflammation of the skin. As a result of the physical and chemical insults that skin covered by absorbent articles must endure, substantial work has been done to deliver compositions to the skin from the absorbent articles. Desirably, the compositions preserve the skin""s own barrier function. However, the compositions can also repair or restore barrier function to skin that has been damaged.
Disposable absorbent articles such as diapers, training pants, adult incontinence products, underpants, feminine care products and nursing pads have been used to absorb body fluids and leave the skin dry. Disposable absorbent articles of this type generally include a liquid impermeable backsheet member, an absorbent core or assembly, and a liquid permeable body facing or liner material. The body facing or liner material comes into contact with the wearer""s skin. While the body facing material is made of a soft, compliant material, the material rubs against the skin during use and may not leave the skin completely dry and free of the bodily fluids, such as solid or semi-solid waste, the absorbent article is trying to absorb. During frequent insults of bodily fluids and frequent use of disposable absorbent articles, the skin can become irritated and appear red and be sore to the touch.
Substantial efforts have been made to provide skin care compositions on the bodyfacing surfaces of disposable absorbent articles. The efforts have focused on providing skin care compositions on the bodyside liners of such articles because the bodyside liner typically has the greatest surface area coming into contact with the skin of the wearer of the article. Frequently, the benefits perceived to be obtained from the skin care compositions are only realized if the skin care composition is transferred to the skin of the wearer of the article. Hence, the desire to apply the compositions to the portion of the article having the greatest area of contact with the skin. It is also known to provide skin care compositions on the containment flaps, leg elastics, waist elastics and other portions of absorbent articles that come into direct contact with the wearer""s skin.
Application of skin care compositions to absorbent articles has been known since the early 1970s. In the 1990s, efforts shifted to describing compositions that would remain where they were originally applied and that would not migrate to other portions of the article. U.S. Pat. No. 5,643,588 (issued on Jul. 1, 1997 to Roe et al.) describes a disposable diaper having a lotion coating on the topsheet of the diaper. The lotion coating is described as including an emollient and an immobilizing agent; the immobilizing agent prevents the flow or migration of the emollient into the diaper. The emollient is described as including petroleum-based, fatty acid ester type, alkyl ethoxylate type, fatty acid ester ethoxylates, fatty alcohol type, polysiloxane type or mixtures of such emollients. Suitable immobilizing agents are described as including C14-C22 fatty alcohols, C12-C22 fatty acids, C12-C22 fatty alcohol ethoxylates having an average degree of ethoxylation ranging from 2 to about 30, waxes and mixtures of such ingredients.
The Roe patent describes the emollient in the lotion coating as having a plastic or fluid consistency at 20 deg. C. and as tending to flow or migrate into the interior of the diaper. Roe et al. describe that this migration of the emollient into the interior of the diaper can cause undesired effects on the absorbency of the diaper core due to the hydrophobic characteristics of many of the emollients. Roe et al also recognize that migration of the emollient in the lotion coating means that much more emollient has to be applied to the diaper topsheet. Increasing the quantity of emollient that must be applied not only increases the cost, but also exacerbates the undesirable effect on the absorbency of the diaper core. Roe et al. go on to recognize that the immobilizing agent counteracts this tendency of the emollient to migrate or flow by keeping the emollient primarily localized on the surface of the diaper topsheet.
Separate efforts have been made to identify compoundsxe2x80x94distinct from those that could be considered xe2x80x9cemollientsxe2x80x9d or xe2x80x9cimmobilizing agentsxe2x80x9dxe2x80x94capable of reducing lotion migration. U.S. Pat. No. 6,149,934 (issued to Krzysik et al. on Nov. 21, 2000) describes an absorbent article having a lotion formulation on the bodyside liner of the article where the lotion formulation includes an emollient, a wax and a viscosity enhancer. Krzysik et al. describe the viscosity enhancer component as helping to stabilize the formulation on the bodyfacing surface of the bodyside liner in order to reduce migration and to improve transfer to the skin. Krzysik et al. describe suitable viscosity enhancers as including polyolefin resins, lipophilic/oil thickeners, ethylene/vinyl acetate copolymers, polyethylene, silica, talc, colloidal silicone dioxide, zinc stearate, cetyl hydroxy ethyl cellulose, other modified celluloses and mixtures of such compounds.
The need for compositions that remain on and do not migrate away from the liner (and other bodyfacing surfaces) of absorbent articles has been well recognized. However, as work in the area of composition formulation continues, the compositions tend to increase in their complexity (for example, the number of ingredients). For a number of reasons, it would be beneficial to reduce the number of ingredients used in skin care compositions formulated for application to absorbent articles. Benefits include better quantification of individual ingredients in the blend, reduced handling and processing of individual ingredients and reduced cost associated with elimination of ingredients. Therefore, there remains a need for a skin care composition for application to the bodyfacing surfaces of absorbent articles having a simplified formula but still delivering the performance need of stability on the surfaces to which it is applied.
In response to the difficulties and problems discussed above, compositions having simplified formulations and good stability (despite not containing an immobilizing agent) have been discovered. While the compositions of the inventions can have a variety of applications, the compositions are particularly beneficial when used in conjunction with absorbent articles such as diapers, incontinence garments, feminine care products, training pants, diaper pants, nursing pads and wound dressings. A further benefit of the compositions of the invention is that the compositions have viscosities and penetration hardnesses comparable to compositions that include immobilizing agents. The purposes and advantages of the present invention will be set forth in and apparent from the description that follows, as well as will be learned by practice of the invention. Additional advantages of the invention will be realized and attained by the compositions and articles particularly pointed out in the written description and claims hereof, as well as from the appended drawings.
In one aspect, the present invention relates to an absorbent article that includes an outer cover, a bodyside liner, an absorbent body and a composition. The bodyside liner is typically liquid permeable and defines a bodyfacing surface. The bodyside liner is connected in a generally superposed relation to the outer cover. The absorbent body is located between the bodyside liner and the outer cover. The composition is on a portion or the entire bodyfacing surface of the bodyside liner. The composition can be generally solid, semi-solid or liquid. The composition may be in a variety of forms, including, but not limited to, emulsions, lotions, creams, ointments, salves, suspensions, gels and the like. The composition can be applied to the bodyside liner using a variety of techniques including foam application, spraying, slot coating and printing. The present invention also encompasses technology that would permit integration of the composition directly with fibers or other materials used to form the bodyside liner. The compositions can be applied to the bodyfacing surface in amounts of from about 0.1 grams per meter squared (g/m2) to about 30 g/m2. The compositions of the invention could also be applied to or be present on other skin contacting surfaces of absorbent articles such as the waist and leg elastics and the containment flaps.
The compositions of the invention can include from about 40 to about 99 percent by weight of one or more emollients. More specifically, the compositions include from about 60 to about 95 percent by weight of emollient(s). Emollients are skin conditioning ingredients that help to soften, smooth, plasticize, lubricate, moisturize, improve the appearance of, improve the feel of and protect the skin. Even more specifically, the compositions include from about 75 to about 90 percent by weight of emollient(s). Suitable emollients include petrolatum; partially hydrogenated vegetable and animal oils; fatty acid esters having a melting point greater than 30xc2x0 C.; alkyl silicones having a melting point greater than 30xc2x0 C.; lanolin; triglycerides having a melting point greater than 30xc2x0 C. and mixtures thereof.
The compositions of the invention can also include from about 1 to about 60 percent by weight of one or more compounds acting as stability enhancers that increase the meltpoint viscosity of the emollients of the composition. More specifically, the compositions include from about 5 to about 40 percent by weight of one or more stability enhancers. Even more specifically, the compositions include from about 10 to about 25 percent by weight of stability enhancer(s).
Examples of suitable stability enhancers include polyolefin resins, ethylene/vinyl acetate copolymers, polyethylene, silica, silica silylate, silica methyl silylate, alkyl hydroxy ethyl cellulose, quaternary starch compounds, natural clays, synthetic analogs of natural clays, organically modified clays, quaternary modified clays, colloidal silicone dioxide, magnesium aluminum silicate, polymethacrylate polymers, polystyrene copolymers and mixtures thereof.
The compositions of the invention do not include compounds that are understood to act as immobilizing agents for the emollients. Until now, it was believed that in order to prevent the migration of the emollient(s) away from the bodyside liner of the article it was necessary to include an immobilizing agent in the composition. Compounds that have been recognized as immobilizing agents include C14-C22 fatty alcohols, C12-C22 fatty acids, C12-C22 fatty alcohol ethoxylates having an average degree of ethoxylation ranging from 2 to about 30 and waxes. It is believed that the immobilizing agents stabilized the emollients by increasing the melting point of the compositions in which they were included. The increase in melting point led to an increased viscosity at a given temperature. It is believed that the stability enhancers of the invention can perform the function previously performed by the immobilizing agents by contributing to the viscosity of the composition (as opposed to increasing the melting point). Unexpectedly, the compositions of the invention have physical properties similar to conventional compositions containing immobilizing agents.
The compositions of the invention can also include from about 0.1 to about 59 percent by weight of natural fats or natural oils. More specifically, the compositions can include from about 5 to about 45 percent by weight of natural fats or natural oils. Desirably, the compositions of the invention include from about 10 to about 30 percent by weight of natural fats, natural oils or mixtures of both. Natural fats and oils include fats, oils, essential oils, fatty acids, fatty alcohols, phospholipids and mixtures of these compounds. The natural fats and oils can be similar to the lipids that are present in healthy skin in order to mimic the naturally present lipids. Synthetic or synthetically modified fats and oils could potentially also be used if they functioned in the same manner as their natural counterparts.
The compositions can also include sterols, sterol derivatives or mixtures of both in an amount of from about 0.1 to about 10 percent by weight. Sterols and sterol derivatives include compounds such as xcex2-sterols with a tail on the 17 position and no polar groups, such as cholesterol, C10-C30 cholesterol/lanosterol esters, tall oil sterols, soy sterols, sterol esters and mixtures of these compounds. More specifically, the compositions include from about 0.5 to about 5 percent by weight of sterols, sterol derivatives or mixtures of both. Even more specifically, the compositions include from about 0.8 to about 1 percent by weight of the sterol compounds.
In addition to the components already described, the compositions of the invention may also include active ingredients such as those ingredients that may be useful for treating skin irritations such as diaper rash. Examples of such active ingredients include allantoin and its derivatives, aloe, aluminum hydroxide gel, calamine, cocoa butter, cod liver oil, dimethicone, glycerin, kaolin and its derivatives, lanolin and its derivatives, mineral oil, petrolatum, white petrolatum, shark liver oil, talc, topical starch, zinc acetate, zinc carbonate, zinc oxide and mixtures of these ingredients. Some of the ingredients listed as possible active ingredients for treating the skin can also be used as emollients.
Ranges are used to describe the relative quantities of compounds in the compositions of the invention and ranges are used to describe the relative physical properties of the compositions of the invention. It is understood that the ranges are by way of illustration only and that one of skill in the art would recognize that the nature of the specific compositions dictates the levels to be applied to achieve the desired results. The levels of components are ascertainable by routine experimentation in view of the present disclosure.
The compositions of the invention typically have a melting point of from about 32xc2x0 C. to about 100xc2x0 C. Melting behavior in this range provides compositions that are relatively immobile and localized on the bodyfacing surface of the bodyside liner of the absorbent article at room temperature. Though relatively immobile and localized at room temperature, the compositions are also readily transferable to the wearer of the article at body temperature through natural rubbing or friction during wearing and through adhesion of the composition to the skin of the wearer. The compositions also maintain their integrity and are not completely liquid at elevated temperatures such as may be experienced during storage. Stability in a solid state at elevated temperatures is made possible, in part, by the increase in viscosity provided by the stability enhancers. Desirably, the compositions of the invention are easily transferable to the skin by way of normal contact, including adhesion of the composition to the skin, wearer motion or body heat. Because the compositions are relatively stable on the bodyfacing surfaces of the articles, the quantities of the compositions necessary to provide the desired skin barrier benefits are reduced. In addition, special barrier or wrapping materials may not be necessary for the articles of the invention.
The compositions of the invention have high shear viscosities of greater than about 40 centipoise at processing temperatures such as at a temperature of about 60xc2x0 C. or higher. The melting points and, therefore, the processing temperatures vary for different compositions of the invention. The compositions may also have a penetration hardness of from about 2 millimeters to about 100 millimeters at 25xc2x0 C.
In another aspect, the compositions of the invention demonstrate improved stability on the bodyside liners of the absorbent articles. More specifically, when the compositions of the invention contain about 10% or more of stability enhancer(s), the compositions exhibit less than 10% loss from a bodyside liner material. Further, when the compositions of the invention contain about 10% by weight or less of stability enhancer(s), the compositions exhibit less than about 20% loss from a bodyside liner material.
The absorbent articles and compositions of the invention advantageously deliver the benefits of conventional skin care compositions provided on absorbent articles but with simplified formulations. The skin care compositions of the invention provide a vehicle for delivering emollients that soothe and protect the skin without the need for an immobilizing agent. Further, by not needing an immobilizing agent, the skin care compositions of the invention have more formulation flexibility; for example, greater quantities of skin care active ingredients could be used to provide more efficacious compositions. It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the invention claimed. The accompanying drawings, that are incorporated in and constitute part of this specification, are included to illustrate and provide a further understanding of the articles and compositions of the invention. Together with the description, the drawings serve to explain the various aspects of the invention.